Hawk's Eggs can be harvested from hawks' nests. Hawks' nests look like other birds' nests which can be found throughout Skyrim, but you can tell the difference before seeing their name by the hawk feathers which may be lying next to them.

You can reach these nests with a tower-style addition, or by using Whirlwind Sprint from a proper position for either property. You can also climb up the rocks next to Lakeview Manor and jump to the roof.